The invention relates to fuel cells and more particularly to solid oxide fuel cells capable of utilizing a hydrocarbon as a source of fuel.
In general, hydrogen gas or mixtures of hydrogen and other gases have been the primary fuel supplied to the anode of solid oxide fuel cells. In some instances, hydrogen has been produced by the gasification of coal or steam reforming of liquid or gaseous hydrocarbon fuels in operations external to the cell. In addition to requiring expenditures for separate processing equipment by the external process, reforming of hydrocarbons further involves an endothermic reaction and therefore requires the addition of heat to the process.
An internal reforming process within the cell would have certain advantages. Heat generated by the electrochemical reaction at the anode catalyst to provide hydrogen ions could be used to supply at least a portion of the heat required by the reforming process. Equipment and space requirements could be reduced. However, some internal processes and reforming catalyst materials have limitations.
If the reforming process is separated from the electrochemical process, a means of transferring heat between the processes must be provided. If the anode catalyst is used both for reforming and the electrochemical conversion, its performance under reforming conditions is generally limited. As an illustration, nickel is a common anode catalyst and has some reforming properties. However, under reforming conditions, nickel on alumina will sinter and tend to form enlarged crystals thereby reducing the effective surface area of the catalyst both for reforming and as an anode catalyst.
Accordingly, one object of this invention is a fuel cell capable of using hydrocarbons as a fuel. A second object of the invention is a fuel cell with internal reforming of hydrocarbons supplied to the fuel cell. Another object of the invention is a fuel cell with internal reforming of hydrocarbon fuels with means to provide effective heat transfer between the reforming and electrochemical operations. These and other objects will become apparent from the following description.